The present invention relates to processes for transmitting low-frequency acoustic waves in a liquid by means of electro-acoustic transducers of the double-tonpilz type and transducers which implement these processes. The technical sector of the invention is that of the construction of electro-acoustic transducers.
Known in the prior art are electro-acoustic transducers, especially piezo-electric transducers, referred to as double-tonpilz transducers, which comprise a rigid cylindrical box, open at both ends and, inside the said box, disposed coaxially with the latter, two identical electro-acoustic drivers, for example two stacks of piezo-electric plates which are in line and located on both sides of a central counter-mass and between two horns. The outer faces of the two horns are located in the plane containing axial ends of the box, so that they are in contact with the liquid in which the box is immersed.
The outer faces transmit acoustic waves in the liquid when the electro-acoustic drivers are excited electronically. These double-tonpilz transducers are used in particular for transmitting low-frequency acoustic waves in the water in a given direction.
One of the problems posed by this type of transducers is the elimination of the acoustic waves transmitted by the near faces of the horn.
A solution to this problem consists in using sealed boxes filled with gas. This solution entails the necessity for the box of withstanding the immersion pressures which can be high-level pressures.
Another solution consists in placing at the rear of the horns static masses or dampers referred to as "baffles" which absorb the rear radiation.